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Strabismus & Ocular Motility > Management of Incomitant Deviations > Flashcards

Management of Incomitant Deviations Flashcards

1
Q

What do we need to know from the investigation into incomitant deviations?

A

Diagnosis
- Paresis (some muscle movement so a -1 to -3 on OMs)
- Paralysis (-4+ on OMs)

Level of Incomitance
- Muscle Sequelae
- Secondary larger than Primary deviation

Differential Diagnosis
- Acquired vs. Congenital
- Recent vs. Longstanding

Symptoms
- Diplopia
- Pain
- Ptosis
- Reduced VA
- Nystagmus
- Other

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2
Q

What symptoms do we need to know about diplopia?

A
  • Constant or Intermittent
  • Direction (Horizontal, Vertical or Torsional)
  • Largest Separation of Images (in what gaze position, near or distance or both fixation distances)
  • Relieve Diplopia by Closing 1 Eye? (Monocular diplopia often comes from cataracts)
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3
Q

What symptoms do we need to know about in incomitant strabismus?

A

Pain
- When & which position?

Reduced/Loss VA
- Colour vision
- Contrast sensitivity
- Visual field defect

Ptosis
- Complete/Partial

Nystagmus
- Type & direction
- Constant or intermittent
- Oscillopsia (seen in recently acquired strabismus where the world wobbles.

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4
Q

How long should we observe for in incomitant strabismus?

A

To allow time for spontaneous recovery before surgery you should allow for 9 - 12 months of observation and for ocular motility to be stable for at least 3 months

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5
Q

What 3 methods do we have for reliving or minimising diplopia?

A
  • Teach AHP
  • Prisms
  • Occlusion
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6
Q

What is the aim of an AHP?

A

To move the eyes away from the field of action of the paresed muscle and to move the eyes to a position where the deviation is least

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7
Q

What are the aims of prism use in managing incomitant deviations?

A
  • Aim of prisms is to restore prism using the smallest prism amount
  • Move the image into suppression area if potential BSV absent
  • To further separate the images if there’s no BSV potential or suppression area
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8
Q

What does the type of prism depend upon in managing incomitant deviations?

A
  • Direction of diplopia
  • Constant/ intermittent diplopia
  • Distance(s) appreciate diplopia
  • Position(s) of gaze appreciate diplopia
  • Duration and stability of deviation
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9
Q

What options are there for prism use in managing incomitant deviations?

A
  • Temporary – Fresnel prisms
  • Permanent – incorporate prisms
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10
Q

How should we fit prisms when using them to manage incomitant deviations?

A
  • Full lens
  • Distance or reading glasses only
  • Upper segment or bifocal segment
  • Split prisms
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11
Q

What are the disadvantages of Fresnel prisms?

A
  • Horizontal magnification
  • Vertical magnification
  • Curvature of vertical lines (less so in prisms incorporated into glasses)
    Asymmetric horizontal magnification
  • Change in vertical magnification with horizontal angle
  • Chromatic Dispersion
  • Dynamic Visual Acuity (DVA)
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12
Q

What does ‘Chromatic Dispersion’ lead to?

A

Part of the disadvantages of Fresnel prisms

  • Diffraction of light by grooves in Fresnel prism
  • Cause reduced contrast
    Effect VA, contrast sensitivity, fusion and stereoacuity
    Reduction substantial if prism >10∆
  • 10∆ prism (Kulnig, 1987)
    Incorporated into glasses: reduce VA to 6/9 (~0.15 logMAR)
    Fresnel prisms: reduce VA to 6/12 (0.30 logMAR)
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13
Q

What is ‘Dynamic Visual Acuity’ (DVA)?

A
  • The ability to discriminate an object when there is movement between object and individual
  • DVA is increasingly reduced as fresnel prism strength increased

Identification of orientation of a moving Landolt C viewed at 57cm (Maconachie et al. 2010)

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14
Q

What did Knight & Griffiths (2011) find about Fresnel Prisms?

A

Driving standard require VA between 0.2-0.3 logMAR
In photopic condition using >15 dioptre prism participants should not be driving
In mesopic conditions using >5 dioptres participants should not be driving

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15
Q

What are the advantages of Fresnel prisms?

A
  • Orientation of prism has no effect on VA and contrast sensitivity (Veronneau-Troutman, 1978)
  • Lightweight
  • Easily changeable
  • May relieve AHP
  • May allow return to work & ability to do daily tasks
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16
Q

How do we fit Fresnel prisms?

A
  • Draw outline slightly smaller than edge of lens using non-permanent marker pen
  • Place under water
  • Apply prism to back surface of lens
    If very high curvature (high myopic correction) apply to front surface
  • Remove air bubbles by wiping/pressing in apex to base direction
17
Q

When should we incorporate prisms?

A
  • Stable angle of deviation (after observation period)
  • Comfortable in prisms
    Reasonably concomitant
  • Power of prism relatively small (<8 PD either eye)
  • Surgery contraindicated
18
Q

What problems do we have with incorporating prisms?

A

Weight and edge thickness

19
Q

How successful are prisms in CNIV palsy?

A
  • Prisms useful if relatively small vertical deviation in P.P. and fairly concomitant
  • Full correction of angle often required to relieve diplopia
    Exception: longstanding with extended vertical fusion range
20
Q

What is the exception to using fully correcting prisms in CNIV palsy?

A

Exception: longstanding with extended vertical fusion range

21
Q

How successful are prisms for managing CNVI palsy?

A
  • Prisms useful if minimal/small amount of lateral incomitance
  • Typical prism prescribed for horizontal deviations is generally 50% of the total deviation
22
Q

When are prisms most successful for treating incomitant deviations?

A
  • Successful use of prisms more likely if realistic patient expectations
  • Frequent follow-up,
  • Patient >65 years
23
Q

What did the Diplopia impacts on patients’ health related quality of life (HRQOL) study from Hatt et al (2014) study?

A

Hatt et al (2014) performed a retrospective study including 34 patients (aged 14-84 years) with diplopia

Aim: determine if successful treatment of diplopia improve HRQOL

Method: two questionnaires pre-prism treatment and at follow up

  1. Diplopia questionnaire: rate severity of diplopia (5-point scale)
  2. Adult strabismus questionnaire: four areas
    Self-perception
    Reading
    Interactions
    General function
24
Q

What did the Diplopia impacts on patients’ health related quality of life (HRQOL) study by Hatt et al (2014) find?

A

Results: 23 of 34 were successfully treated with prisms

  • 74% were prescribed Fresnel prism and 26% had prisms incorporated
  • Significant improvement in
    1. Diplopia questionnaire
  1. Adult strabismus 20 questionnaire
    Improvement in general and reading function
    Unchanged for self-perception and interactions
25
Q

How is PAT / Diagnostic Occlusion used in CNVI palsy?

A

Aim: determine the true angle of deviation

Advocated for longstanding unilateral SO palsy

Prism Adaptation
Method:
Fully correct angle of deviation with prisms for 1-2 weeks
Perform PCT on return to determine if angle has increased

Diagnostic occlusion
Method:
Occlude the paretic eye (non-fixing eye) for 1 day - 2 weeks FT.
Perform PCT before occlusion and on return without allowing binocular vision

26
Q

What does Occlusion used in managing incomitant deviations depend on?

A
  • Constant/ intermittent diplopia
  • Position(s) of gaze appreciate diplopia
  • Duration and stability of deviation
27
Q

What are the options of occlusion?

A
  • Blenderm
  • Bangerter Foils
  • Frosted Lens
  • Occlusive Contact Lens
28
Q

How can we fit occlusion options?

A
  • Total occlusion
  • Lower or upper segment occlusion
  • Sector occlusion (primarily used in 4th nerves)
29
Q

What outcomes could there be after the observation period in managing incomitant deviations?

A
  • Recovered
  • Stable
  • Deteriorated
30
Q

What ocular factors affect the management of incomitant deviations?

A
  • Severity of symptoms
  • Duration since onset
  • Presence and size of AHP
  • Binocular functions
  • Torsion
  • Appearance

Strabismus & Ocular Motility (8 decks)

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